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My engine No is Y8--1250. What is it.
Are the inlet and exhaust valves the same. If not whats the difference in general terms. Bigger, smaller, longer etc
Mike 8) 8) 8)
Engine is a 557cc H31-8 side valve model from late 1931. This model was much used by the Post Office.
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Hi Julian.
Thanks again for that. But--this is an OHV engine.
Mike 8) 8) 8)
You have a mystery engine!
Y8 prefix definately for the H31-8 according to BSA.
Hi Mike
Assuming the 500cc is similar in construction to the 550 , on the overhead valve engines if you screw the valve tappet guides into the crankcases they slope in towards each other on the side valve they are vertical so this could perhaps tell you if you have a side valve crankcases . I tried to find out awhile back if you can fit overhead valve head etc onto side valve cases some said you could some said you couldn't but no one really seemed to know for sure if your engine was running before you got it then yes it must be able to be done . I only found out about the slope of the tappet guide by having two different sets of crankcases on the bench at the same time hope this helps regards Mark
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Hi Julian.. I never doubted the veracity of your information and indeed am simply surprised. So we shall try to delve more deeply into the mystery.
Hi Mark, after reading post from Julian I was beginning to think along the same lines. I have no idea if or when it was last running, but when it was purchased it was in "one piece" so I guess that it must have run. We shall find out eventually. I shall keep you in the loop as things progress.
Mike 8) 8) 8)
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If anyone can assist I would like to know if the conrods are the same for both motors.
This "mystery" would probably begin to explain why the crankshaft is mis-alligned. Someone has probably stripped it to change the conrods and done a bad job of reassembly.
Whatever---it certainly shows signs of having run. Of course another possibility is that someone has shoved an OHV motor in and re-stamped the number. How naughty????.
So there we go gents any light you can maybe throw on this will be gratefully accepted.
By the way chevvy big bore valves are 1.72" across the face and I believe that sloper is 1.75". Thats a difference of 030".
More eventually
Mike 8) 8) 8)
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OK :), the thick plottens. Just checked this out and the tappet guides definitely slope in toward each other, Thus the cases appears to be OHV. About the Engine Number---No idea. It all points to being OHV so my guess at the mo is that someone(maybe the post office) restamped the engine--this No appears to have been PO. I understand that it was not unheard of for this to be done with replacement engines and indeed frames.
So back seeking advice????????????/
Mike 8) 8) 8)
Mike
Can you see any casting numbers on the rod, cases, covers etc?
Julian
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Hi Julian. Must confess have not looked very deeply at the mo but I know that there is a No on the crankshaft. Will do a more thorough inspect later in the week.
Ever so confused. comic.
Mike :( 8) 8) 8)
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:) :) :)Hi Agen Julian
I have found the following numbers on the motor.
on the flywheel(crank) 24-821 and ?4-821. I assume that they are both the same. Nothing at all on the conrod.
On timing side? casing 24-1276. also on opposite casing apparently ----4122 or 4L22
On cylinder barrel 1712 or 1312. No prefix numbers.
And that is that.
Mike 8) 8) 8)
Mike
I think you timing side crankcase half casting is a 1932 part. The part number in the book is for the casting with fixed fittings. These numbers usually one different to the casting number. Cant make anything of the other numbers.
The H32- 9 SV part is 24 1277.
The S32 - 8 OHV part is 24 1275.
Both these had 3/4 inch gudgeon pins while the H31-8 had a 5/8 pin - according to the Hepolite catalogue.
The H31-8 was being sent out from the factory as late as June 1932.
Not sure if this takes the mystery any further forward.
Hi Mike
Looked at my crank and the numbers on the flywheels are24–321 is it possible you've missed read the 8 for a 3 , they're out of a 1930 overhead valve
Conrod as the number 24–281 on it and as Julian says it should be a three quarter inch gudgeon pin . The conrod measures 23.5 cm but could only measure that with a tape measure
In my parts book for 1930 and for 1931 The flywheels are the same part number for the overhead valve models for both years
There is a different part number for the flywheels for the side valve
there are 2 x 4 digit numbers on the crankcases just above the oil fill they are the same number on both of my cases and I'm assuming it's for them being a matching pair of cases
There are no numbers on the barrel
My valves also measure 1.75 inches
Hope this helps
Mark
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Hi Agen..
Anything is likely. I will look again at all these No's and see if I have mis read them. N]and measure the gudgeon pin. We appear to be getting somewhere even if not very fast. No sweat.
Mike 8) 8) 8) 8)
Hi Mike
I had a bit of a daft idea but thought I'd try it so went in garage where I've got 1930 side valve and 1930 OHV cases so tried putting them together , when pushed together the OHV timing side and side valve drive / engine number side don't quiet join up tight at rear of engine but are very close and would take very little work to make them join correctly . The front end does join up and all bolt holes appear to line up the only obvious sign of them being wrong was a difference in the shape of the castings under the magneto mounting plate . When I joined the side valve timing side case to the OHV drive / engine number side they fitted fine again casting differences under the mag plate .
So it could be possible that in the past someone has joined a side valve drive side case with the side valve numbers on it to an overhead valve timing chest side I only spent 15 mins on it and I could be wrong but it may help explain your dilemma .
So does anyone know if this is possible?
Mark
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Hi Mark.
Thanks for that and I'll look at all those points as I go along. I now seriously believe that this is an OHV engine that has been r-stamped or stamped Y8 in error for Y9. Dunno.
Going forward I shall treat it as Full OHV and hope that I dont come across something a bit radical along the way.
I haven't yet measured the gudgeon pin, but it was all together so I guess its correct for this particular beast. What diameter piston should it have for the OHV 500cc. It now just a case of offering up to see what fits properly where.
By the way I bought a pair of Chevvy valves and they are en-route although at this stage I don't know if I'll need new valves, but @ $25.00 the pair inc postage I just took a chance.
Mike 8) 8) 8)
Hi Mike
Piston should be 80 mm in diameter as standard
The valves are certainly cheap enough and hopefully you won't need them , it's a shame I have no ability at machining otherwise I think I would go down that line as well
Good luck with the rebuild hopefully you won't find any more problems
Mark
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Haven't stripped the head yet, but I imagine that it will probably/possibly need new guides and maybe??? new seats. If thats the case then having it redone to fit the other valves will be of very little extra cost. Only maybe the cost of (I believe) shortening the valve stems and and machining the collett grooves. Will keep you in the loop.
Mike 8) 8) 8)
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I am now assuming that for whatever reason I have an OHV with a suspect No. Not a problem it all seems to point that way
Question is what would the part No of the piston be. The piston I have states +.030" which would make +/-80.75mm when new. It actually measures at about 79.6mm. Assuming the measurement to be accurate thats about .055" wear add to that the barrell wear (not measured). lets also assume that my maths are fair. That piston is going to be seriously sloppy.
I know there are several options that I can pursue and in truth I am looking for the easiest/most cost effective. The requested part No is a good launch point.
Your advises please. I have now received my new gasket set
Mike 8) 8) 8)
Mike
The parts books for 1931 and 1932 only list +1mm oversized. +30 may be Hepolite - there may be a part number inside on the skirt.
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I was talking pistons today with a very clued up piston man and he told me that it is possible to fit an 80mm MG piston into the 500cc Sloper. Needs quite a bit of machining and bushing but evidently successful.
Anyone know of this. Its shown on the VMCC site. Members/registered only and I dont really wish to be on yet another site.
Regards
Mike 8) 8) 8)
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Hi Mark
Crankshaft stamp24-321 as you suggested, not 24-821 as stated earlier.
Mike 8) 8) 8)